1. Field of the Invention
The present invention relates to a closed-type electrically-driven compressor, and more particularly to a closed-type electrically-driven compressor employing a high pressure chamber system used for refrigerators and air conditioners.
2. Description of the Prior Art
A closed-type electrically-driven compressor employing a conventional high pressure chamber system will be described below with reference to FIGS. 4 to 6.
FIG. 4 is a cross sectional view showing a structure of a closed-type electrically-driven compressor of the prior art, FIG. 5 is a cross sectional view of a main portion of a cylindrical body and a cover body in a general closed-type electrically-driven compressor popular of the prior art and FIG. 6 is a cross sectional view showing an essential part of the prior closed-type electrically-driven compressor with its cover body deformed due to an internal pressure.
The closed-type electrically-driven compressor shown in FIG. 4 is structured such that a compressing mechanism portion 10 and an electric motor portion 20 driving the compressing mechanism portion are received within a cylindrical body 30, which constitutes a main body of a closed container, a refrigerant sucked from a refrigerant suction pipe 40 is compressed in the compressing mechanism portion 10 and then discharged into the cylindrical body 30 (the closed container) from a refrigerant discharge port 11 provided in the compressing mechanism portion 10 to be filled in the cylindrical body 30 and then discharged from a discharge pipe 41. The closed container is constructed (a high pressure chamber system) such that internal pressures are caused by the refrigerant to act thereon in operation.
The cylindrical body 30 shown in FIG. 4 is substantially formed in a cylindrical shape, and is provided with a cover body 31 which sealing the cylindrical body 30. The cover body 31 is formed by press work of a steel sheet. Further, a terminal 50 is fitted in a hole formed in the cover body 31 to be welded to the cover body 31. Since the refrigerant exerts internal pressures on the cover body 31 during operation as mentioned above, it is necessary to ensure a pressure resisting strength against a high pressure in operation. As a countermeasure thereof, it is generally known as an ideal configuration to form the cover body substantially in a spherical shape.
However, such spherical-shaped cover body increases a length of the closed container of the compressor to increase a space in the refrigerant equipment, into which the compressor is mounted. Further, in the case of mounting on the cover body the terminal 50 for supplying electricity to the electric motor portion 20, which drives the compressing mechanism portion 10, and the pipes 40 and 41 for circulating the refrigerant and the like, there are caused problems with espect to weldability, assembling quality, formability of the cover body itself and the like. Then, as shown in FIG. 5, the cover body 31 employs a substantially flat configuration to improve productivity.
A structure of the closed container having the substantially flat cover body and shown in FIG. 5 will be described hereinbelow.
The reference numeral 30 denotes a cylindrical body which constitutes a main body of the closed container, and the compressing mechanism portion 10 and the electric motor portion 20 are received within the cylindrical body 30, which is not shown in the drawing. The reference numeral 31 denotes a cover body, which is fixed to the cylindrical body 30 through a welded portion 32 to form a container of the closed-type compressor. The reference numeral 50 denotes a terminal, which is fixed to a hole formed on an upper surface of the cover body 31 through a welded portion 51.
Further, a terminal pin 52 for supplying electricity to the electric motor is provided inside and outside the terminal 50. The reference numeral 40 denotes a refrigerant suction pipe, which is fixed to the cover body 31 of the cylindrical body 30 through a welded portion 41. The reference numeral 60 denotes a pin for securing of a cover covering the terminal 50, which is fixed to the cover body 31 of the cylindrical body 30 through a welded portion 61.
Incidentally, Japanese Utility Model Publication Nos. 64-1495 and 3-57318 disclose a prior art with respect to the container of prior closed-type compressors.
Such prior closed-type compressors present the following problems in the structure of their cover.
In recent years, it has been necessary to employ an alternative refrigerant in refrigeration and air conditioning equipments for the purpose of preventing an ozone layer from being broken, and the substitutive refrigerant includes a refrigerant, typified by refrigerant R-410A, which involves a pressure about 1.5 times that of the conventional refrigerant under the same temperature condition.
When such refrigerant involving a high pressure is used to operate the compressor having the conventional closed container as shown in FIG. 5, internal pressures acting on the cover body 31 tend to deform a substantially flat portion into a spherical shape as shown in FIG. 6. Accordingly, since a central portion of the cover body 31 is tensioned in a radial direction, it is made thin in thickness. Further, since a force tending to strip off the welded portion 51 between the cover body 31 and the terminal 50 or the welded portion 41 between the cover body 31 and the refrigerant suction pipe 40 is increased more than the conventional manner, problems of leakage of the refrigerant are liable to occur.
Then, increasing a thickness of the cover body may be adopted as means for solving the problem, investigation reveals that the thickness of the cover body 31 should be increased to about 2.5 times the conventional thickness in order to stand an increase of the pressure amounting to about 1.5 times that with the conventional refrigerant. Therefore, there are caused problems that the cover body can not be easily formed by press work of a steel sheet and it is increased in weight.